Preheat the oven to 375°F. Line two baking sheets with parchment paper.

In a large bowl, whisk together the flour, baking powder, and salt. Make a well in the center and add the olive oil and water. Stir until a shaggy dough forms.

Knead the dough gently in the bowl or on a lightly floured surface until it comes together into a smooth ball. If the dough feels dry, add a teaspoon of water at a time. If it's sticky, dust lightly with flour.

Divide the dough into two equal portions. Working with one portion at a time makes it easier to roll the dough very thin.

On a lightly floured surface, roll the dough as thin as possible, about 1/16 to ⅛ inch thick. For the crispiest crackers, aim for paper-thin dough. Transfer the rolled dough to the prepared baking sheet, keeping it in large slabs.

Brush the surface lightly with egg wash. Sprinkle evenly with your desired toppings, pressing larger toppings gently into the dough so they adhere during baking.

Bake for 10 to 12 minutes, or until the crackers are golden brown around the edges and dry in the center. Thin spots may brown a little more quickly, which adds to the artisan look.

Allow the baked slabs to cool on the pan for about 5 minutes. Break them into rustic pieces by hand, then transfer to a cooling rack to cool completely.

Store the cooled crackers in an airtight container at room temperature for up to one week.